Magnesium base casting alloy



March 17, 1964 G. s. FOERSTER ETAI. 3,125,444-

MAGNESIUM BASE CASTING ALLOY Filed April 3, 1963 Magnesium INvENToRs. George 5. F o erser Francis L. Burke HTTORNEYS United States Patent 3,125,444 MAGNESIUM BASE CASTING ALLOY George S. Foerster, Midland, and Francis L. Burkett, Breckenridge, Mich., assiguors to The Dow Chemical 3,125,444 Patented Mar.l 17, 1 964 In preparing the alloy of the present invention, magnesium is melted under a suitabie halide flux cover using conventional melting and ailoying techniques as practiced in :the magnesium art, and the copper and aluminum 5 added thereto as small ingots or chunks at a temperature Compangllgl georNpg'rtg Delaware suiiicient to dissolve said additions, such as, for example, 6 Chinn (CL 75 168) a temperature of from 1250 to about 1350" P. The alloy so prepared may be cast into ingots suitable for This invention relates to alloys of magnesium and remelting and casting or cast directly ater preparation particularly concernsamagnesium blasetalioy having pa-r- 10 into desired cast articles. In casting, the so-prepared -tieular utility as a casting alloy. melt is preferably cast in a heated mold having the de- The object oi the present invention is to provide a sired cavity configuration, the mold being heated to a magnesium base alloy having improved castability and temperature of from about 300 to about 700 F. or mechanical properties thus having particular utility as more, such that premature solidification during pouring a casting alloy. in the smaller and irregular channels, if any, in the mold In general, the above and other objects and advantages cavity will not occur prior 'to completion of pouring and have been Ifound obtainable by adding to molten magsubsequent withdrawal of the heat source from the mold. nesium both aluminum and copper, each Within a par- After the mold is fil-led and the heating means withdrawn ticulalr concentration range. therefrom, lthe metal in the mold is allowed to cool Accordingly, the allo-y of the present invention coinsuicently to solidify. The solidified Icast article is then prises bnoadlylan amount of aluminum by Weight of trom removed from the mold. In addition, if desired, the 5 to about 20 percent and an amount of copper by weight so-cast -anticle may be subsequently solution heat treated of lfrom 4 to about 10 percent, the balance being magand aged to enhance strength. nesiurn. Specifically, however, the composition orf the The lalloy of the present invention may be cast into present alllo-y is gnaplrically illustrated in the accompany- `sand or permanent molds, or employed in operations ing dnawing, and thus conveniently determined therefrom. using a cold-mold die casting apparatus as commonly In the drawing there is shown on a conventional triused in the die casting art. angular coordinate graph the percent aluminum, percent The following examples serve to further illustrate the copper and percent magnesium in the alloy. The alloy present invention. composition thus represented lies in a broad composition Various magnesium base Ialloys containing aluminum area land includes lan area of preferred proportions, said and copper were prepared according to the present inareas being fur-ther defined below. vention, each having a composition as indicated .in Table The amounts of aluminum and copper, the balance I, by melting commercial grade magnesium at a teinby diiference being magnesium, which have been Ifound :penalture of about 1300 F. under a suitable hal-ide flux satisfactory in the 'alloy of the present invention are 35 cover and adding thereto small chunks of the said shown graphically, las mentioned above, in the single aluminum and copper. A suitable halide ux cover, for figure of the drawing, the parallelogram ABCD thereof, example, is one comprising about 34% KCl, about 31% bounded by' MBPS AB, BC, C1? '51nd Dd, referring 'O the MgCl2, about 12% CaF2, about 13% MgO, and about broad' COMPOSIOP Tang@ Wllhm Which th@ afofsald 10% BaCl2. A permanent mold having the cavity conmPTOVed PTOPeFtW/S 0f. he Present alloy me @maimed- 40 figur-ation of a 1A inch diameter round test bar was heated The Pff/femm? wmposmqn range 0f the psnt'lloy to a tempenature ocE about 540 F. and the prepared s 'also Shown m Said drawmg as ama DEEG W'lthm tha alloys cast therein. These bars were then tested for above paralllelogram ABCD, bounded lines DE, EF, percent elongation (percent E) (using a 2 inch ganga FG apd Gimsaid lrefepabl C10 mposmon area fogne' 4, section), tensile strength `(TS), and tensile yield strength Spondmg am' @meal y n.1 genm'a to an amount o mm o (TYS) (at a 0.2% offset) in the as-east condition, after about 5 to about 16 weight percent ralunnnum, and an Q l he t tm t d f l 1 ,d he t t amount of from about 5 to about 10 Weight percent ou on. a @ea en" ain a ter, Sou on a treacopper the balance being magnesiumment with subsequent aging, at the temperatures and In addition, small amounts of other alloying constittunes as indicated m Table I which m addmon Sms uents conventionally employed may be used in the forth the results of these tes/ ahoy provided it ds not Sigrcamly ,impair ,the im It should be lunderstood that other heat treatments proved castabilityof the alloy obtained under the present and agmg COHN'JIOHS man 111056 Indicated 1H Table I invention can be employed with respect to the alloy of the present The term magnesium, as referred to herein, means the iHVCIlOIl in Order t0 Obtain, for example, greater age pure meta-l and alloys thereof having less than about 1.0 hardening :and higher strength.

Table I After Solution Heat After Solution Heat Composition 1 As Cast Treating for 16 Hrs. Treating and Aging at 750 F 24 Hrs. at 350 F.

Example 1,000 p.s.l. 1,000 p.s.i. 1,000 p.s.i. Percent Percent Percent Percent Percent A Cu E TYS Ts TYS TS TYS TS 9.2 5.8 2.o 1o 27 0.8 17 29 2.0 16 26 6. 3 8. 7 1. 0 15 24 1. 0 15 21 0.5 15 22 15. o 6.0 o. 5 24 26 0. 5 2o 2s 0. 5 27 31 15. 0 9. 6 0.5 25 2s 0. 5 22 26 0.5 24 33 1 Balance, magnesium. percent ot other alloyin-g constituents therein either as additions or as unavoidable impurities.

Among the advantages of the :alloy are that it has the lightweight characteristic of magnesium, the molten alloy flows easily into and completely fills casting molds of intricate shape producing castings having la high strength to weight ratio, and is composed of readily available metals.

We claim:

1. A magnesium base alloy consisting essentially of 'aluminum and copper and magnesium, said alloy having a composition by weight within the composition range represented by the `area ABCD of the graph in the appended drawing bounded by lines AB, BC, CD, and DA.

2. A magnesium base alloy consisting essentially of aluminum and copper `and magnesium, Iin proportions represented by the area DEFG `of the gnaph in the appended drawing and bounded by lines DE, EF, FG and GD.

3. A magnesium base alloy consisting essentially of about 9.2 weight percent aluminum, `and about 5.8 weight percent copper, the balance being magnesium.

4. A magnesium base alloy consisting essentially of about 6.3 weight percent aluminum, and about 8.7 weight percent copper, the balance being magnesium.

5. A magnesium base 'alloy consisting essentially of about 15.0 weight percent aluminum and about 6.0 weight percent copper, the balance being magnesium.

6. A magnesium base Ialloy consisting essentially of about 15.0 weight percent aluminum yand about 9.6 weight percent copper, the balance being magnesium.

References Cited in the file of this patent UNITED STATES PATENTS 1,729,339 Gann Sept. 24, 1929 1,793,023 Schmidt Feb. 17, 1931 2,314,024 Topping Mar. 16, 1943 FOREIGN PATENTS 293,359 Great Britain Ian. 31, 1929 

1. A MAGNESIUM BASE ALLOY CONSISTING ESSENTIALLY OF ALUMINUM AND COPPER AND MAGNESIUM, SAID ALLOY HAVING A COMPOSITION BY WEIGHT WITHIN THE COMPOSITION RANGE 